scholarly journals Changes in glacier volume on Mt. Gongga, southeastern Tibetan Plateau, based on the analysis of multi-temporal DEMs from 1966 to 2015

2019 ◽  
Vol 65 (251) ◽  
pp. 366-375 ◽  
Author(s):  
BO CAO ◽  
BAOTIAN PAN ◽  
WEIJIN GUAN ◽  
ZHENLING WEN ◽  
JIE WANG
Keyword(s):  
General Rule ◽  
Rate Of Change ◽  
Glacier Surface ◽  
Digital Elevation ◽  
Multi Temporal ◽  
Glacier Ice ◽  
The Mean ◽  
Hydrological Cycles ◽  
Key Indicators ◽  
Gongga Mountains

ABSTRACTThe accelerated retreat of glaciers and the reduction of glacier ice reserves caused by climate change can significantly affect regional water resources and hydrological cycles. Changes in glacier thickness are among the key indicators that reflect this process. We analyzed changes observed in the elevation of glacier surfaces in the Gongga Mountains (GGM) using multi-temporal Digital Elevation Models (DEMs) derived from topographic maps, SRTM, ICESat and ZY-3 data. The results showed that the mean rate of change in glacier surface altitude in the GGM was ~−26.7 ± 2.03 m (0.54 ± 0.04 m a−1) between 1966 and 2015. The mean melt rates differed over different time periods, latterly showing an accelerating trend. As a general rule, glaciers appear to be losing more volume at lower than at higher elevations. Further analysis of these results suggests that supraglacial debris coverage in the GGM promotes higher rates of mass loss.

scholarly journals Surface and bed morphology of Hansbreen, a tidewater glacier in Spitsbergen

2012 ◽  
Vol 33 (2) ◽  
pp. 111-138 ◽  
Author(s):  
Mariusz Grabiec ◽  
Jacek Jania ◽  
Dariusz Puczko ◽  
Leszek Kolondra ◽  
Tomasz Budzik
Keyword(s):  
Drainage System ◽  
The Arctic ◽  
Medium Size ◽  
Glacier Surface ◽  
Bed Morphology ◽  
Digital Elevation ◽  
Tidewater Glacier ◽  
The Mean ◽  
Tectonic Features ◽  
System Geometry

Surface and bed morphology of Hansbreen, a tidewater glacier in SpitsbergenHansbreen, a medium size tidewater glacier in Southern Spitsbergen (Svalbard) is one of the most intensively studied glaciers in the Arctic. This work presents new digital elevation models of its surface and basal topography based on data collected during GPS/GPR campaigns conducted in the spring seasons of 2005 and 2008, as well as on other recent topographic/bathymetric sources. The mean thickness of the glacier is calculated as 171 m and its volume is estimated to be 9.6 (±0.1) km3. The main feature of the bedrock morphology is a vast depression that is overdeepened below sea level and extends as far as 11 km upstream from the glacier front. This depression is divided into four individual basins by distinct sills that are related to the main geological/tectonic features of the area. The bedrock morphology affects considerably the glacier's surface topography. The influence of bedrock and surface relief on the subglacial drainage system geometry is discussed. Vast depressions on the glacier surface favor concentration of meltwater and development of moulin systems.

scholarly journals Glacier changes from a new inventory, Nianchu river basin, Tibetan Plateau

2009 ◽  
Vol 50 (53) ◽  
pp. 87-92 ◽  
Author(s):  
Caiping Zhou ◽  
Wenbin Yang ◽  
Liang Wu ◽  
Shiyin Liu
Keyword(s):  
Tibetan Plateau ◽  
Surface Area ◽  
River Basin ◽  
Glacier Surface ◽  
Air Temperatures ◽  
Digital Elevation ◽  
Glacier Changes ◽  
Southern Tibetan Plateau ◽  
The Mean ◽  
Topographical Maps

AbstractThe ice cover of the Nianchu river basin, southern Tibetan Plateau, was mapped for 2005, using a SPOT5 scene, and for 1990 and 2000 from Landsat TM/ETM. Digital elevation models (DEMs) were generated from 1 : 50 000 scale topographical maps. The results show that in 2005 there were 136 glaciers in this basin, with a total area of 224 km2. Of these, 37 glaciers had an area >1 km2 and 10 were larger than 5 km2; the average snout altitude was 5608m a.s.l. A comparison of outlines from the last 15 years shows that most glaciers have decreased in size; none have advanced. From 1990 to 2005, Xiaquepu glacier No. 56 and Shimozongpu glacier No. 38 retreated 310 and 560 m, respectively. The mean reduction in glacier surface area was 5% (10 a)–1 while the area of glacial lakes expanded by 10%; nine new lakes formed in this basin over the 15 year period. Because air temperatures here have been increasing, while precipitation has remained steady, glacier retreat is considered to be related to rising temperature.

Multi-temporal mass balance changes of the Northern Patagonian Icefield from 1975 to 2016

2020 ◽  
Author(s):  
Etienne Berthier ◽  
Ines Dussaillant ◽  
Fanny Brun ◽  
Vincent Favier
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Shuttle Radar Topography Mission ◽  
Ice Age ◽  
Aerial Photographs ◽  
Digital Elevation ◽  
Multi Temporal ◽  
The Mean ◽  
Military Institute ◽  
Year 2000

<p align="justify">The northern Patagonian Icefield (NPI) is the second largest ice mass in Patagonia (3740 km²). Estimation of recent volume changes confirm an acceleration of ice loss in the last decades compared to the mean mass loss since the Little Ice Age. However, Icefield-wide responses at shorter time scales (5-25 yrs) are still poorly documented and not well understood.</p><p align="justify">We compare five digital elevation models (DEM) acquired between 1975 and 2016 over the NPI: SPOT6 and SPOT7 DEMs for year 2016, SPOT5-HRS DEMs for 2012 and 2005, the Shuttle Radar Topography Mission DEM (SRTM) for year 2000 and the earlier Chilean military institute cartography (IGM) derived from aerial photographs acquired in 1975. We derive cefield-wide mass balances during four different time periods (1975-2000, 2000-2005, 2005-2012, 2012-2016). Our results suggest an acceleration of mass loss from 1975 to 2016. Although error bars are large, we suggest a shift from moderately negative icefield-wide mass balance rates before 2000 (of the order of -0.6 m w.e. yr<sup>-1</sup>), towards larger mass losses during the first decade of the 21<sup>st</sup> century(of the order of -0.8 m w.e. yr<sup>-1</sup>) and even more negative value from 2012 to 2016 (-1.2 ± 0.2 m w.e. yr<sup>-1</sup>).</p><p align="justify">But these results must be considered cautiously. The 1975-2000 map of elevation change shows a thickening rate of over 1 m/yr which are not supported by image analysis. We stress the need to construct a revised 1975 NPI topography in order to document the NPI mass balance observations back to 1975 with improved confidence.</p>

scholarly journals Multi-Temporal Arable Land Monitoring in Arid Region of Northwest China Using a New Extraction Index

2021 ◽  
Vol 13 (9) ◽  
pp. 5274
Author(s):  
Xinyang Yu ◽  
Younggu Her ◽  
Xicun Zhu ◽  
Changhe Lu ◽  
Xuefei Li
Keyword(s):  
Arable Land ◽  
Ground Truth ◽  
Northwest China ◽  
Hexi Corridor ◽  
Ground Truth Data ◽  
Land Protection ◽  
Promising Tool ◽  
Study Results ◽  
Multi Temporal ◽  
The Mean

Development of a high-accuracy method to extract arable land using effective data sources is crucial to detect and monitor arable land dynamics, servicing land protection and sustainable development. In this study, a new arable land extraction index (ALEI) based on spectral analysis was proposed, examined by ground truth data, and then applied to the Hexi Corridor in northwest China. The arable land and its change patterns during 1990–2020 were extracted and identified using 40 Landsat TM/OLI images acquired in 1990, 2000, 2010, and 2020. The results demonstrated that the proposed method can distinguish arable land areas accurately, with the User’s (Producer’s) accuracy and overall accuracy (kappa coefficient) exceeding 0.90 (0.88) and 0.89 (0.87), respectively. The mean relative error calculated using field survey data obtained in 2012 and 2020 was 0.169 and 0.191, respectively, indicating the feasibility of the ALEI method in arable land extracting. The study found that arable land area in the Hexi Corridor was 13217.58 km2 in 2020, significantly increased by 25.33% compared to that in 1990. At 10-year intervals, the arable land experienced different change patterns. The study results indicate that ALEI index is a promising tool used to effectively extract arable land in the arid area.

scholarly journals The volume coefficients of expansion of several gases at pressures below one metre

1934 ◽  
Vol 143 (850) ◽  
pp. 487-505 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Linear Function ◽  
Rate Of Change ◽  
Linear Extrapolation ◽  
Satisfactory Explanation ◽  
Volume Coefficient ◽  
Temperature Ranges ◽  
The Mean ◽  
Permanent Gases ◽  
Limiting Value

There have not appeared recently any new determinations of the rate of change of the volume coefficient of expansion of condensable gases at pressures in the neighbourhood of a half to one metre. The work of Henning and Heuse and Heuse and Otto has been confined to a study of the permanent gases, their results leading to the conclusion that up to a pressure of 1 metre the rate of change of either the pressure or volume coefficient is a linear function of the pressure. Our knowledge of the behaviour of the condensable gases in this connection rests almost entirely on the very careful work of Chappuis, who in 1907 made a series of accurate determinations of the volume coefficient of expansion of carbon dioxide at a series of pressures from 1500 mm. to 500 mm. and over several temperature ranges. The investigation led to one unexpected conclusion which Chappuis left largely unexplained. On linear extrapolation to zero pressure of the graph of pressure against the mean coefficient of expansion over temperature intervals 0-20º, 0-40º, 0-100ºC., the limiting value of the coefficient rose from the normal value of 0.003661 for the 0-20º determinations to 0.003671 for those made over the range 0-100ºC. Chappuis concludes "that condensation on the reservoir surface plays a part in the irregularities but it is difficult to obtain a satisfactory explanation." As far back as 1853 Magnus demonstrated that the adsorption of sukphur dioxide on glass was sufficient to affect measurements of the expansion coefficient of gasses, and the importance of this error was recognized by Chappuis who in 1879 applied a correction to Regnault's measurements. Richards and Mark and Baly and Ramsay have pointed out the necessity for a knowledge of the amount of adsorption on the walls of the containing vessels when undertaking such determinations.

Precise computation of the direct and indirect topographic effects of Helmert's 2nd method of condensation using SRTM30 digital elevation model

2011 ◽  
Vol 1 (4) ◽  
pp. 305-312 ◽  
Author(s):  
Y. Wang
Keyword(s):  
Standard Deviation ◽  
Digital Elevation Model ◽  
Outer Zone ◽  
Mean Value ◽  
Constant Density ◽  
Topographic Effects ◽  
Topographic Effect ◽  
Digital Elevation ◽  
The Mean ◽  
Elevation Model

Precise computation of the direct and indirect topographic effects of Helmert's 2nd method of condensation using SRTM30 digital elevation modelThe direct topographic effect (DTE) and indirect topographic effect (ITE) of Helmert's 2nd method of condensation are computed using the digital elevation model (DEM) SRTM30 in 30 arc-seconds globally. The computations assume a constant density of the topographic masses. Closed formulas are used in the inner zone of half degree, and Nagy's formulas are used in the innermost column to treat the singularity of integrals. To speed up the computations, 1-dimensional fast Fourier transform (1D FFT) is applied in outer zone computations. The computation accuracy is limited to 0.1 mGal and 0.1cm for the direct and indirect effect, respectively.The mean value and standard deviation of the DTE are -0.8 and ±7.6 mGal over land areas. The extreme value -274.3 mGal is located at latitude -13.579° and longitude 289.496°, at the height of 1426 meter in the Andes Mountains. The ITE is negative everywhere and has its minimum of -235.9 cm at the peak of Himalayas (8685 meter). The standard deviation and mean value over land areas are ±15.6 cm and -6.4 cm, respectively. Because the Stokes kernel does not contain the zero and first degree spherical harmonics, the mean value of the ITE can't be compensated through the remove-restore procedure under the Stokes-Helmert scheme, and careful treatment of the mean value in the ITE is required.

scholarly journals Electrical Behaviour of Finely Divided Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 173-191 ◽  
Author(s):  
J. G. Paren ◽  
J. W. Glen
Keyword(s):  
Relaxation Times ◽  
Surface Adsorption ◽  
Frequency Dispersion ◽  
Polar Regions ◽  
Electrical Behaviour ◽  
Heterogeneous Nature ◽  
Glacier Ice ◽  
Bulk Relaxation ◽  
Adsorption Of Co ◽  
The Mean

Abstract The electrical behaviour of ice which has been finely ground and compressed was investigated during ageing in air and over a range of temperatures. The dielectric behaviour may be accurately represented as the sum of two elliptical relaxation spectra. The behaviour eventually stabilizes with similar activation energies for the mean relaxation time of each spectrum c. 0.25 eV, and the ratio of the relaxation times is ten in samples of density c. 0.42 Mg m-3. Arguments are presented on whether the higher-frequency dispersion is a consequence of the heterogeneous nature of the samples or is a bulk relaxation process. The similarities between the behaviour of such finely ground ice and of deposited snow and polar glacier ice are discussed. The extent to which the results may be attributed to surface adsorption of CO2 are examined by reference to measurements of the CO2 content of finely divided ice and ice from polar regions.

scholarly journals Characterization of Canadian High Arctic glacier surface albedo from MODIS C6 data, 2001–2016

2017 ◽  
Author(s):  
Colleen A. Mortimer ◽  
Martin Sharp
Keyword(s):  
Large Scale ◽  
Surface Albedo ◽  
Temporal Trends ◽  
Principal Component ◽  
High Arctic ◽  
Shortwave Radiation ◽  
Glacier Surface ◽  
Annual Variations ◽  
The Mean ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract. Inter-annual variations and longer-term trends in the annual mass balance of glaciers in Canada's Queen Elizabeth Islands (QEI) are largely attributable to changes in summer melt. The largest source of melt energy in the QEI in summer is net shortwave radiation, which is modulated by changes in glacier surface albedo. We used measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors to investigate large scale spatial patterns and temporal trends and variability in the summer surface albedo of QEI glaciers and their relationship to observed changes in glacier surface temperature from 2001 to 2016. Mean summer black-sky shortwave broadband albedo (BSA) decreased at a rate of 0.029 ± 0.025 decade-1 over that period. Larger reductions in BSA occurred in July (−0.050 ± 0.031 decade-1). No change in BSA was observed in either June or August. Most of the decrease in BSA, which was greatest at lower elevations around the margins of the ice masses, occurred between 2007 and 2012 when mean summer BSA was anomalously low. The First Principal Component of the 16-year record of mean summer BSA was well correlated with the mean summer North Atlantic Oscillation Index, except in 2006, 2010, and 2016. During this 16-year period, the mean summer LST increased by 0.046 ± 0.036 °C yr-1 and the BSA record was negatively correlated (−0.64, p 

scholarly journals Ultrasonic Heating Detects Lipiodol Deposition within Liver Tumors after Transarterial Embolization: An In Vivo Approach

Biology ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 901
Author(s):  
Natsuhiko Saito ◽  
Toshihiro Tanaka ◽  
Kiyoyuki Minamiguchi ◽  
Ryosuke Taiji ◽  
Hideyuki Nishiofuku ◽  
...  
Keyword(s):  
Sound Velocity ◽  
Temperature Coefficient ◽  
Rat Liver ◽  
Liver Tumors ◽  
Transarterial Embolization ◽  
Rate Of Change ◽  
Accumulation Ratio ◽  
Ct Value ◽  
The Mean

Computed tomography (CT) is the standard method to evaluate Lipiodol deposition after transarterial embolization (TAE) for a long period. However, iodine but not Lipiodol can be observed on CT. A minimally invasive other method to detect Lipiodol has been needed to evaluate accurate evaluation after procedure. The purpose of this study was to evaluate the efficacy of using the rate of change in sound velocity caused by ultrasonic heating to reflect Lipiodol accumulation after TAE in a rat liver tumor model. We analyzed the association of this developed technique with CT images and histological findings. Eight rats bearing N1S1 cells were prepared. After confirmation of tumor development in a rat liver, Lipiodol was injected via the hepatic artery. Seven days after TAE, CT scan and sound velocity changes caused by ultrasonic heating were measured, and then the rats were sacrificed. An ultrasonic pulse-echo method was used to measure the sound velocity. The temperature coefficient of the sound velocity in each treated tumor was evaluated and compared with the mean CT value and the histological Lipiodol accumulation ratio. Pearson’s correlation coefficients were calculated to assess the correlation between the measured values. The correlation coefficient (r) of the mean CT value and histological Lipiodol accumulation ratio was 0.835 (p = 0.010), which was considered statistically significant. Also, those of the temperature coefficient of the sound velocity and the histological Lipiodol accumulation ratio were statistically significant (r = 0.804; p = 0.016). To our knowledge, this is the first study that reported the efficacy of ultrasonic heating to detect Lipiodol accumulation in rat liver tumors after TAE. Our results suggest that the rate of change in sound velocity caused by ultrasonic heating can be used to evaluate Lipiodol accumulation in liver tumors after TAE, and thus could represent an alternative to CT in this application. This new innovative technique is easy to treat and less invasive in terms of avoiding radiation compared with CT.

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